A flight control device serves to control the movements of an aircraft on the basis of movements imposed by the pilot on a control stick that is connected to said flight control device. Nevertheless, and in particular with a convertible aircraft, the pilot must not pilot the aircraft in the same way when the aircraft is in a stage of flight proper, and when it is in a stage of landing or taking off, thereby making the task of piloting more complex.
In order to assist the pilot, it is thus known to provide a flight control device comprising a mount, a lever pivotally mounted on the mount to pivot about at least one axis of rotation and designed to be secured to the control stick of the aircraft, and mechanical means for generating a return force on the lever about the axis of rotation, said means comprising a spring and a motor member that are arranged in such a manner that a first end of the spring is constrained to move in rotation with the lever and a second end of the spring is constrained to move in rotation with an outlet shaft of the motor member.
As a result, when the lever is moved by the pilot, the spring is stressed by a movement of its first end relative to its second end, thereby generating a return force on the stick. The return force as generated in this way serves to limit the movements imposed by the pilot on the control stick and thus to limit the movements of the aircraft. By modifying the position of the second end of the spring relative to the first end of the spring with the help of the motor member, it then becomes possible to move the anchor point of the spring and thus to modify the force relationship of the spring, i.e. the relationship that defines the forces exerted by the mechanical means for generating a return force on the lever. Under such circumstances, it is possible to modify the force return that is generated for the benefit of the pilot depending on the stage in which the aircraft is to be found: a stage of flight proper, or a stage of taking off or landing. The pilot is thus guided in piloting the aircraft by the flight control device.
Nevertheless, changing the force relationship of the spring by means of the motor member when the pilot is already imposing a movement on the spring via the lever generates a change to the anchor point of the lever that is not necessarily desirable for the pilot. The anchor point remains the point of equilibrium between the stage of flight and workload on the pilot.